Is there any way I can log back into an old Xbox 360 account without the email/password and...

Hello Xeno98989! I'm Kris and I'd be happy to help you with your question.

You can try using the recovery form however, Microsoft have to be able to verify you and if they don't have enough details to confirm you are the account owner, then they won't let you have access.

You can find the form here https://account.live.com/acsr

I have an old Xbox account and idk the email or password and I'd like to get it back

Youd need to somehow figure out what email you used. There isnt any way to get an account back without at least knowing the email associated with the account.

Child accounts on Xbox one/series have email attached, it's impossible to have an account profile without having email

That email and password will be necessary to log in the Xbox 360 guide inside the game

Will this require me to log back into my Xbox account. If so I don’t know my password and don’t have access to my old email the Xbox was created in

I was able to fix this. Read the inability to log into Uplay was on old accounts. You need to add an email/password into it. All I did was pop in AC2 on my 360 (I still had it) and go into Uplay from the game. Went into my account options and sure enough
there was no email assigned to my name. Added it in along with a password. I switched back to the Xbox One and loaded up AC4. Sure enough problem solved.